A typical application has some settings: if an application logs, a
setting is the path to the log file. If an application sends email,
there are settings to control how email is sent, such as the email
address of the sender.

Applications that serve as frameworks for other applications may have
settings as well: the transaction_app defined by
more.transaction for instance has settings controlling
transactional behavior.

Morepath has a powerful settings system that lets you define what
settings are available in your application and framework. It allows an
app that extends another app to override settings. This lets an app
that defines a framework can also define default settings that can be
overridden by the extending application if needed.